There isnt' any /focus in Classic and there are multiple discussions on the negative implications of that for pets, especially multiple/all pet parties.

I think a Hunter Pet with mend pet (which also cleanses) can be the most resilient but running multiple hunters can be problematic due to dead zones.

I would at least take a healer (ideally a Priest who can do an AoE heal or an AoEish heal like Chain Heal from a Shaman). A healer should help the pets last longer and/or allow you to rez folk and helps enable the use of Life Tap.